This core will provide two fundamental benefits to the various telomere/telomerase projects. First, it will conserve resources by preventing unnecessary duplication of routine assays that may need to be performed by several of the participating groups. Secondly, it will achieve greater consistency between experiments that arise from the investigations of the research groups. The assays provided by this core are as follows: * To isolate and assay the telomerase activity in S100 extracts and freeze-thaw extracts from cultured tumor cells, hybrid cell lines, and tumors taken directly from patients. * To test whether telomerase activity is inhibited by various agents that are generated from Program l, Program 2. Program 3, the Chemistry Core, and from outside collaborative sources (N.C.I.), using our established procedures or the rapid assays proposed in program l. * To evaluate the growth inhibitory activity of telomere/telomerase interactive agents. * To determine telomere length. * To determine the number of dicentric chromosomes in cells. * To assess the clonogenic survival of tumor cells.